The present invention relates to a dry etching method, and it further relates to a method of fabricating a semiconductor device.
In recent years, the scale of semiconductor device integration has been improved dramatically. Lithography technology, which is now playing an important role in improving the scale of semiconductor device integration, requires finer formation of patterns. With a view to meeting such a requirement, a light source with a shorter wavelength has been used. Currently, KrF excimer laser lithography is a dominant technique in the field of lithography technology. In such a photolithography process step, it becomes necessary to achieve reductions in the thickness of photoresist films that are formed on substrates upon which process steps are performed, to achieve higher resolution.
A reactive dry etching technique with a C.sub.4 F.sub.8 plasma has been employed to form contact holes in silicon dioxide films. One problem of the dry etching method is that the etching selectivity ratio, which means the ratio of the etching rate of the silicon dioxide film (R2) to that of the photoresist film (R1)(i.e., R2/R1), is low. Low etching selectivity ratios cause a photoresist film to become reduced in thickness during an etching process, resulting in partially etching a silicon dioxide film masked with the photoresist film. If such undesired etching occurs, then there occurs a short circuit between interconnect lines therefore causing considerable damage to the fabrication yield and reliability of semiconductor devices.
Bearing in mind the aforesaid problems with the prior art techniques, the present invention was made. Accordingly an object of the present invention is to provide a dry etching method capable of providing improved etching selectivity ratios to the photoresist film and a method of fabricating a semiconductor device employing such a dry etching technology.